#include <bits/stdc++.h>
using namespace std;
const int N = 1e5+5;
int n, m, d;
vector<int> keep[N];
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> d >> m;
for( int i=1;i<=m;i++ )
{
int a; cin >> a;
keep[a].push_back( i );
}
int l = 0, r = n-d;
while( l<r )
{
int mid = (l+r)/2;
int temp = 0, cnt = 1;
for( int i=1;i<=n-d;i++ )
{
for( auto x : keep[i] )
{
if( temp+1 > mid )
{
temp = 0;
cnt++;
}
temp++;
if( cnt > i+d )
{
cnt = n;
break;
}
}
if( cnt > i+d ) break;
}
if( cnt > n-d ) l = mid+1;
else r = mid;
}
cout << l << "\n";
int temp = 1;
for( int i=1;i<=n-d;i++ )
{
for( int x : keep[i] )
{
cout << x << " ";
if( temp+1 > l )
{
temp = 1;
cout << "0\n";
}
else temp++;
}
}
for( int i=0;i<d;i++ ) cout << 0 << "\n";
return 0;
}
